Need some form of battery, it's easy to over produce power, but when you switch from day to night your power generation shuts down for a moment, and hydrogen doesn't pick up the slack...
Start hit points and start damage become irrelevant after a certain point, perhaps they need a cap, or perhaps be disabled after that point is reached...
I like the test idea, however I have already planned for dealing with hordes of zombies, and have trap designs for the eventuality of a zombie apocalypse, the hardest part for me would be dealing with other survivors, they would have to follow my directions, or I would feed them to the zombies myself... Here's a trap idea for you, build a trellis out of iron, dismantle a lawn mower, reassemble the motor and blade from the trellis, at roughly 5' height, toss the mower deck in the scrap pile, the noise from the mower will attract the zombies into a whirling blade of head chopping goodness...
Why, why the mini games, very annoying to have to switch between three different control schemes, with no real pause between them, so go from the z/x time wheel attack, to the arrow time attack, to a click multiple times time attack, to a timed click time attack, here's a game for you, lets pretend someone with only one hand is trying to play...
 "Power The Grid - Speedrunner"){kind=icon}
 "Arcalona"){kind=icon}
 "Idle Evolution"){kind=icon}
 "Immortal Hero Idle"){kind=icon}
 "Ultimate Zombie Quiz"){kind=icon}
 "AntiVillain (-OneShot-)"){kind=icon}